- In Serbia, on the western flank of the German XXII Reserve Corps the advance of 26th Division brings it into contact with the Austro-Hungarian 53rd Division of XIX Corps, held short of Obrenovac since its initial crossing of the Save River. The arriving Germans turn the flank of the Serbian defenders, who pull back and allow the trapped Austro-Hungarians to finally break out. To the east, the German 105th Division of IV Reserve Corps breaks through Serbian positions in the hills east of Lucić, suffering heavy casualties to overcome the fierce enemy resistance. Meanwhile, however, the Germans score a coup when 232rd Reserve Regiment of 107th Division captures a Serbian patrol and an engineer detachment with orders to destroy the railway bridge over the Mlava River to the south. Intelligence gleaned from the prisoners allow the Germans to capture the bridge intact, which will aid further advances. To the south, while the Bulgarian 1st Army continues to be held up in the mountain passes east of Niš, to the south the Bulgarian 2nd Army has made much more progress, and today reaches the Vardar River at Veleš and cuts the railway linking Niš and Salonika.
- Both Russia and Italy formally declare war on Bulgaria today.
- The Serbian government has been pressuring General Sarrail to move his forces north from Salonika and concentrate them at Niš, to oppose the Bulgarians attacking from the east. Sarrail knows that such a movement is impossible with the forces at his disposal, but recognizes that a gesture (beyond the deployment at the Strumica rail station) is needed. As a result, he orders an infantry regiment and artillery battery, newly arrived at Salonika and from the French 57th Division, to move north to Krivolak, on the Salonika-Skopje railway thirty kilometres north of the Strumica rail station and south of Veleš.
|The French advance from Salonika, October 1915.|
- The Italian preliminary artillery bombardment along the lower Isonzo River is joined today by Italian aircraft, which this morning strike the Austro-Hungarian airbase at Aisovizza and begin airstrikes on marching columns and railway stations. These raids are largely unopposed, as the Austro-Hungarian aircraft on the Italian Front are primarily designed for reconnaissance, not aerial combat.
- The government of Japan adheres to the Pact of London today, which had originally been signed on September 5th, 1914 by Russia, France, and Britain and by which they had pledged not to sign a separate peace with Germany. Japan's agreement to remain in the war until the end does not, however, signal an expansion of the Japanese contribution to the war effort of the Entente. Instead, the Japanese government hopes that adhering to the pact will secure it a seat at the peace conference at the end of the war and allow Japanese negotiators to secure the permanent transfer of captured German colonies in Asia and the Pacific to Japan.